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Design for Sound Operated Light Circuit

Discussion in 'Electronic Design' started by Maddy, Aug 29, 2008.

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  1. Maddy

    Maddy Guest

    I am learning morse code. There are software available which convert
    any text into morse and give the output to the headphone jack. I was
    wondering if this sound output at the headphone/speaker jack can be
    used to power a LED or incandescent bulb? Would be thankful if anyone
    can suggest a solution.
  2. JeffM

    JeffM Guest

  3. Frank Buss

    Frank Buss Guest

    You can use your hi-fi system: Use one speaker output for a speaker, if you
    want to hear it and connect a 220 ohm resistor and a LED in series to the
    other output. Adjust balance and loudness that you can hear something in
    the desired loudness and see the LED light, if there is a signal.

    A incandescent bulb is not a good idea, because turning it on and off
    often, will wear away it fast.
  4. + 9V + 9V
    | a |
    LED R3
    | k ----|
    C1 + c | c
    audio line level ----|||-----------b NPN |--b NPN
    | | e Q1 | e Q2
    /// R1 | | |
    | R2 | ///
    | | |
    | /// |

    R1 22k
    R2 82 Ohm
    R3 2k2
    C1 10uF / 3V
    Q1, Q2 transistors: almost any NPN si, for example BC548, BC109, etc.

    This can be run from a 9 V battery.
    It is in fact a very sensitive AC detector.

    Optinally one can connect a capacitor from the collector of Q1 to ground.
  5. GregS

    GregS Guest

    I learned the Morse long ago, but I really don't think I could easily convert
    light to letter very easily. One problem for me would be looking at the light and
    looking at my sheet. I know it would be a huge problem watching several sources
    mixed together.

  6. legg

    legg Guest

    I think you will find that Morse is more easily/quickly comprehended
    audibly (or in mechanically/electrically written text) than visibly.
    In situations where only visible communication is possible, reliable
    Morse transmission speed may be reduced to as much as 1/3 that of
    other methods. It's also visually exhausting for longer messages -
    wearing out the eye's point-perception capacity, quite rapidly.

  7. JeffM

    JeffM Guest

    While I applaud your effort, my intuition is
    1) The OP doesn't know which end of a soldering iron to hold.
    1a) He should be posting ONLY to sci.electronics.basics.

    2) As he is MULTI-POSTING
    from Google, he is quite clueless
    and will see *this* blob (in a proportional font)
    and not know what to do with it.

    3) Even if he knew how to get to a monospaced version, like
    your ASCII technique will likely leave him baffled
    (even if you didn't leave out the characters where junctions are
    supposed to be).

    Frank's answer (and mine) leaning toward COTS stuff
    seems more apt.
    Even Bill Bowden's response in the s.e.b thread
    (to use a step-up transformer) seems over the OP's head.

    That's what the evidence says to me. Of course, I could be wrong.
  8. neon


    Oct 21, 2006
  9. Rich Grise

    Rich Grise Guest

    FWIW, you're one of about two total google posters I've ever seen come
    back to read responses. I think they expect the answers to show up under
    their pillow or something. ;-)

  10. Sure, just for fun, here is the ltspice version

    You will see about 11mA LED current for 1V input @ 1000Hz.
    The LED brightness can be set by the volume control.
    As the pulses are 1000Hz, that seems like constant 'on' during key presses.

    Fun for me to play , if it educates anyone, great.
    He posted to the right group with s.e.d.
  11. JeffM

    JeffM Guest

    Nah. I won't argue with the general sentiment,
    but your arithmetic is off.
    Last time he gave a count, JT had 65 of us whitelisted.

  12. G-Force Platinum from

    Best audio stimulated light show to date.

    Accepts external sources too!
  13. Maddy

    Maddy Guest

    Thanks a lot for the great response. Especially Jan for the circuit.
    As deduced from the evidence, I am a newbie. Dont have much practice
    but do surely know which end of the soldering iron to hold. Need the
    info to help somebody else implement it. However, didnt quite
    understand all the text symbols on the circuit. However, thanks for
    it, I will work it out.
    Thanks again,
  14. LVMarc

    LVMarc Guest

    This can be one and made into a cool product for hearing impaired
    telegraph instruction!

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